Regioselective Transition Metal-Free Catalytic Ring Opening of 2H-Azirines by Phenols and Naphthols; One-Pot Access to Benzo- and Naphthofurans

Abstract

Benzofuran and naphthofuran derivatives are synthesized from readily available phenols and naphthols. Regioselective ring openings of 2H-azirine followed by in situ aromatization using a catalytic amount of Brønsted acid have established the novelty of the methodology. The involvement of a series of 2H-azirines with a variety of phenols, 1-naphthols, and 2-naphthols showed the generality of the protocol. In-depth density functional theory calculations revealed the reaction mechanism with the energies of the intermediates and transition states of a model reaction. An alternate pathway of the mechanism has also been proposed with computer modeling.